Brachytherapy seed cartridges are provided with a number of radioactive brachytherapy seeds, e.g. I-125 or Pd-103 seeds, and used as a supply source of those seeds to be loaded into a seed applicator. The seed applicator is used to implant the seeds within a patient. FIGS. 1 and 2A-C depict a typical seed cartridge 10 manufactured and sold by Mick Radio-Nuclear Instruments, Inc. of Mount Vernon, N.Y., U.S.A. Cartridge 10 includes a magazine 12 and a cap 14. Magazine 12 includes an elongate seed channel 16 for receiving transversely-aligned brachytherapy seeds 18 and dispense aperture 20 from which the seeds are dispensed into the applicator. Cap 14 supports an elongate plunger 22 which is spring-biased to extend into channel 16 and urge the seeds 18 towards dispense aperture 20. Magazine 12 further includes an external helical thread 24 for mating with an internal helical thread, not shown, within cap 14. Cap 14 includes an external thread 26 to secure the assembled cartridge 10 in a V-block for steam sterilization.
To form a disposable, or single-use, cartridge 10, magazine 12 and cap 14 are typically made of a suitable plastic material capable of withstanding steam sterilization. Alteniatively, cap 14 may be formed from stainless steel or brass in order to provide additional shielding. This later feature recognizes that a technician holding a cartridge component in each hand while threading the two components together, due to the proximity of the radioactive seeds to the technician's hands and fingers, presents exposure risks which should be minimized further.
Moreover, the art has seen instances of magazine 12 deforming and/or breaking when a technician applies a tightening torque to cap 14 which exceeds the torsional limit of the plastic magazine 12. Typically, the magazine body is deformed so as to pinch on channel 16 and cause a functionality failure where the seeds will not descend properly under the spring tension of the plunger. The deformed or broken magazine 12 can also lose containment of the radioactive seeds, resulting in a loss of the loaded seeds and a potential hazard to personnel handling the cartridge.